feat: telemetry data integrity — source tagging, UUID fingerprint, duration guards

- Add source field (live/test/dev) to telemetry pipeline: --source flag in
  gstack-telemetry-log, GSTACK_TELEMETRY_SOURCE env fallback, pass-through
  in telemetry-sync, source=eq.live filter on all dashboard queries
- Replace SHA-256 installation_id with UUID install_fingerprint for all tiers
  (not just community). Expand-contract migration: ADD new column + trigger
  to copy installation_id, preserving backward compat with old clients
- Fix duration bug: persist _TEL_START to file via $PPID (stable across bash
  blocks), cap durations at 86400s, reject negative values
- Ungate update-check pings from telemetry=off — sends only version + OS +
  random UUID. Generate .install-id in update-check for telemetry=off users
- Migration 003: source columns, install_fingerprint, duration CHECK
  constraint, indexes, recreated views with source filter, growth funnel
  (first-seen based), materialized views for daily installs + version adoption
- E2E test isolation: session-runner sets GSTACK_TELEMETRY_SOURCE=test
- 8 new telemetry tests (source field, duration caps, fingerprint persistence)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

test/helpers/session-runner.ts

@@ -176,7 +176,7 @@ export async function runSkillTest(options: {
     cwd: workingDirectory,
     stdout: 'pipe',
     stderr: 'pipe',
-    env: { ...process.env, GSTACK_STATE_DIR: testStateDir },
+    env: { ...process.env, GSTACK_STATE_DIR: testStateDir, GSTACK_TELEMETRY_SOURCE: 'test' },
   });
 
   // Race against timeout